In the field of voice and data telecommunications, there is an increasing use of digital communications techniques, allowing increased facilities to be provided to users of a network. However, many users already possess equipment designed for use with an analog network, and so there is a need to allow such users to gain access to the enhanced facilities available on a digital network, without being required to replace their existing equipment.
Thus, for example, there is known a multiplexer, to which analog private exchanges can be connected, and which converts the analog signals to digital signals, and multiplexes them for transmission along a digital line.
There is also known a private branch exchange (PABX), which has modules for connection to both analog and digital equipment, and is also connectable, using a common channel signalling protocol, to a digital network.
However, these known units do not allow the user to take advantage of all of the facilities potentially available on a digital telephone network.
The present invention therefore seeks to provide equipment which overcomes the disadvantages associated with the known units.